JPH06174082A - Travel speed switching device for hydraulic travel vehicle - Google Patents

Abstract

PURPOSE:To enable travel speed to be automatically switched over to high speed and/or low speed, and also enable straight ahead traveling performance to be enhanced. CONSTITUTION:A right and a left hydraulic motor are made to be each variable hydraulic motor, control ports 42 are formed on the upper and lower dead point sides between a first port 40 and a second port 41 in the valve plate 15 of each variable hydraulic motor, and a detection path 49 is provided, to which higher pressure oil is introduced out of the right and left variable hydraulic motors. A switch-over valve 50 is provided, which supplies higher pressure oil from the detection path 49 to one control port 42, and the switch-over valve 50 is designed to be actuated so as to be switched over by means of both spring force and the pressure of high pressure oil, so that travel speeds can thereby be automatically switched over to high speeds and/or low speeds depending on the magnitude of load applied to the variable hydraulic motors during travel.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for switching the traveling speed of a hydraulic traveling vehicle traveling by a left and right traveling hydraulic motor between high speed and low speed.

[0002]

2. Description of the Related Art A variable hydraulic motor is known as a horizontal hydraulic motor for a hydraulic vehicle. This variable hydraulic motor forms a cylinder chamber by inserting a piston into a cylinder hole of a cylinder block that is rotatably supported with a shaft in a housing, and a piston shoe that slides along a rocker cam that supports the piston in the housing. And the cylinder chamber is formed on the valve plate through substantially semicircular first and second ports, and is connected to the hydraulic pressure source and the tank by approximately 180
The pistons expand and contract by the rotation of the cylinder block to discharge and repeat the suction, and the rocker cam is tilted to change the angle so that the piston stroke increases. It is changed to make the rotation speed variable. As a device for tilting the rocker cam described above, for example, the actual open sho 62-16
What is disclosed in Japanese Patent No. 9268 is known. That is, as shown in FIG. 1, the control port d is formed on the valve plate a at the top dead center side between the first port b and the second port c, and the control port d is formed by the two-position switching valve e.・ Second port b,
When the high pressure side port of c and the tank f are controlled to communicate with each other, and high pressure oil is supplied to the control port d, the moment force application point A _{1 of the} piston shifts to the top dead center from the rocker cam tilt center g and the rocker cam tilts. When the control port d is communicated with the tank f, the moment force application point A _{1 of the} piston slightly shifts to the bottom dead center from the rocker cam tilt center g, and the rocker cam tilts back to its original position. In the example shown in FIG. 2, the control port d is formed on each of the top dead center side and the bottom dead center side, and high pressure oil is supplied to the control port d by the two-position switching valve e. If high-pressure oil is supplied to d, the moment force application point A _{1 of the} piston is closer to the top dead center than the rocker cam tilt center g, and if high-pressure oil is supplied to the control port d on the bottom dead center side, the piston moment application point is A ₁ is closer to the bottom dead center than the rocker cam tilt center g, whereby the rocker cam is tilted to the top dead center side and the bottom dead center side.

[0003]

[Problems to be Solved by the Invention] In the former case,
When the control port d communicates with the tank f, the tilting force acting on the rocker cam is weak, the rocking speed of the rocker cam is slow, and the responsiveness deteriorates. In the case of the left and right traveling hydraulic motors, the left and right switching valves e, e Since it is difficult to switch the two at the same time, the straightness becomes worse. . In the latter case, the tilting force acting on the rocker cam increases in both cases, but the high-pressure side port reverses between normal rotation and reverse rotation, so it is guided to the control port during normal rotation and reverse rotation. The high pressure position to be reversed reverses the top and bottom dead center,
Since the rocker cam becomes unstable, it cannot be used as the rotational speed or switching of the traveling hydraulic motor that normally and reversely rotates the variable hydraulic motor when moving forward and backward.

Therefore, an object of the present invention is to provide a traveling speed switching device for a hydraulic traveling vehicle which can solve the above-mentioned problems.

[0005]

The left and right hydraulic traveling motors are variable hydraulic motors, and control ports are provided on the intermediate top dead center side and the bottom dead center side of the first and second ports of the valve plate of each variable hydraulic motor. A detection path to which the higher of the high-pressure oil of the left and right variable hydraulic motors is introduced, and a switching valve that supplies high-pressure oil to one control port by switching the high-pressure oil of the detection path and the spring force What

[0006]

[Operation] The traveling speed can be automatically switched between high speed and low speed by switching the switching valve depending on the size of the load acting on the left and right hydraulic traveling motors while traveling, and the high speed of the left and right hydraulic traveling motors can be changed. Even if the oil pressure is different, the right and left hydraulic traveling motors can be simultaneously switched to the high-speed rotation state and the low-speed rotation state to improve the straightness.

[0007]

[Examples] The left and right traveling hydraulic motors are variable hydraulic motors. As shown in FIG. 3, the variable motor is provided with a cylinder block 4 inside a housing 3 composed of a case 1 and an end plate 2.
Is rotatably arranged, and the shaft 6 is spline-fitted and connected to the spline hole 5 at the center of rotation of the cylinder block 4.
One end of is supported by a bearing 8 in a hole 7 in the bottom 1a of the case 1, and the other end of its shaft 6 is supported by a bearing 10 in a blind hole 9 of the end plate 2 so that the cylinder block 4 rotates together with the shaft 6. It is configured to do. A piston 12 is fitted into a cylinder hole 11 of the cylinder 4 so that the cylinder chamber 1
3, the cylinder chamber 13 is alternately opened at a substantially semicircular first port and a second port (not shown) formed on the valve plate 15 through the port 14 every time it rotates by approximately 180 degrees. A piston shoe 16 swingably connected to the piston 12 is pressed against the front surface of a rocker cam 18 by a shoe retainer 17. The rocker cam 18 has a hole 30 through which the shaft 6 passes, and a rear surface 31 of the rocker cam 18 has a different angle.
-The second stopper surfaces 32 and 33 and the arcuate surface 34 are formed,
The arcuate surface 34 is swingably fitted into an arcuate guide groove 35 formed in the bottom wall 1a of the case 1, and the rocker cam 18
Is tilted to the top dead center side and the first stopper surface 32 is in the case 1
When the front surface of the bottom wall 1a of the rocker cam, that is, the stopper 36 is hit, the angle of the front surface 37 of the rocker cam 18 increases, and the rocker cam 18 tilts toward the bottom dead center side so that the second stopper surface 33 hits the stopper 36. The angle of the front surface 37 of the cam 18 is made smaller.

Next, a device for tilting the rocker cam of the left and right variable hydraulic motor which is a left and right traveling hydraulic motor, that is, a device for switching the traveling speed of the hydraulic traveling vehicle between high speed and low speed will be described with reference to FIG. As shown in FIG. 4, the control ports 4 are provided on the top dead center side and the bottom dead center side in the middle of the first port 40 and the second port 41 in the valve plates 15 of the left and right variable hydraulic motors.
2 are respectively formed, and the pressure oil discharged from the hydraulic pump 43 is supplied to the left and right first and second ports 40 and 41 of the left and right variable hydraulic motors by the operation valve 44 and the brake valve 45. Supply control is performed via 47, the high pressure oil of the first and second ports 40 and 41 is detected by the left and right shuttle valves 48, the higher pressure oil is detected in the detection path 49, and the high pressure oil is switched valve 50. Either control port 42
Is supplied to each. The switching valve 50 is provided on the end plate 2 and is held at the first position A by a spring 51, and the pressure receiving portion 52 is provided.
When the pilot pressure oil is supplied to the pilot type valve, the pilot type valve is switched to the second position B.
The high pressure oil 9 is supplied as pilot pressure oil, and when the high pressure oil reaches or exceeds the set pressure, the second position B is reached.

Next, switching of the traveling speed will be described.
When traveling at high speed, the load of the left and right variable hydraulic motors is small, the pressure of the high pressure oil in the high pressure side port is low, and the high pressure oil in the detection path 49 is lower than the set pressure, so the left and right switching valves 50 are in the first position A. When the switching valve 50 reaches the first position A, high-pressure oil is supplied to the control port 42 on the bottom dead center side, the control port 42 on the top dead center side is connected to the case drain side, and the moment force application point A _{1 of the} piston is rockered. The rocker cam 18 is closer to the bottom dead center than the cam tilt center 15a, and a tilting force closer to the bottom dead center is applied to the rocker cam 18, the second stopper surface 33 contacts the stopper 36, and the angle of the front surface 37 becomes smaller, so that the rocker cam 18 becomes smaller. 18
Since the tilt angle of the cylinder becomes smaller and the stroke of the piston 12 becomes shorter, the flow rate required for one rotation of the cylinder block 4 decreases and the shaft 6 rotates at a high speed.
It becomes a high-speed rotation state. When the traveling load increases in a high-speed traveling state, the load of the left and right variable hydraulic motors increases, and the pressure of the high-pressure oil in the high-pressure side port increases, and the high-pressure oil in the detection path 49 becomes equal to or higher than the set pressure, and the left and right switching valves 50 is the second position II. When the switching valve 50 is in the second position II, high pressure oil is supplied to the control port 42 on the top dead center side, the control port 42 on the bottom dead center side is communicated with the case drain side, and the moment force application point A _{1 of the} piston is rocker. The cam tilt center is closer to the top dead center 15a, and the tilting force closer to the top dead center acts on the rocker cam 18, the first stopper surface 32 contacts the stopper 36, and the angle of the front surface 37 increases, so that the rocker cam 18 becomes larger. Since the tilt angle of 18 becomes large and the stroke of the piston 12 becomes long, the flow rate required for one rotation of the cylinder block 4 increases and the shaft 6 rotates at low speed.

[0010]

The left and right hydraulic traveling motors can be switched between a low speed rotating state and a high speed rotating state depending on the magnitude of the load acting on the left and right hydraulic traveling motors, so that the traveling speed of the hydraulic traveling vehicle can be automatically switched between low speed and high speed. Since the higher pressure oil in the high pressure oil of the left and right hydraulic travel motors is detected and the left and right switching valves 50 are switched at the same time, the left and right hydraulic travel motors are simultaneously switched to the high-speed rotation state and the low-speed rotation state so that the traveling bend does not occur. The straightness is improved.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a rocker cam tilting device for a conventional variable hydraulic motor.

FIG. 2 is an explanatory diagram of a rocker cam tilting device of a conventional variable hydraulic motor.

FIG. 3 is a sectional view of a variable hydraulic motor of the present invention.

FIG. 4 is an explanatory diagram of a traveling speed switching device.

[Explanation of symbols]

1 case, 4 cylinder block, 6 axes, 11
Cylinder hole, 12 piston, 13 cylinder chamber, 1
5 valve plate, 16 piston shoe, 17 shoe retainer, 18 rocker cam, 40 first port, 41 second port, 42 control port, 49 detection path, 50 switching valve, 51 spring.

Claims (1)

[Claims] 1. The left and right hydraulic traveling motors are variable hydraulic motors, and the variable hydraulic motors rotatably support a cylinder block 4 together with a shaft 6 in a case 1, and a piston 12 in a cylinder hole 11 of the cylinder block 4. To form a cylinder chamber 13, the cylinder chamber 13 is sequentially connected to the first port 40 and the second port 41 of the valve plate 15, and the piston shoe 16 connected to the piston 12 is tilted to the top and bottom dead center side. It is assumed that the rocker cam 18 is slidably pressed along the front surface of the rocker cam 18 by the shoe retainer 17, and the top dead center between the first port 40 and the second port 41 of the valve plate 15 of the left and right variable hydraulic motors. Control ports 42 are formed on the point side and the bottom dead center side, respectively, and the high pressure oil on the high pressure side at the first port 40 and the second port 41 is detected. A detection passage 49 which pressure oil higher than the high pressure oil of the left and right variable hydraulic motor it is being introduced, the detection circuit 4
9 high pressure oil is selectively supplied to one control port 42,
Further, the left and right switching valves 50 that connect the other control port 42 to the case drain are provided, and the left and right switching valves 5 are provided.
A traveling speed switching device for a hydraulic traveling vehicle, characterized in that 0 is switched by the pressure of the spring 51 and the pressure of the detection path 49.